Ruby slippers worn by Dorothy in the 1939 movie The Wizard of Oz. Photo: Eric Long/NASM, National Air and Space Museum, Smithsonian Institution.

WASHINGTON, DC.- The Smithsonian museums reported 2009 attendance of 30 million, up from 25 million the previous year. This marks the first time attendance has risen to 30 million since 2001. Admission to all Smithsonian museums in Washington, D.C., is free.

The Smithsonians National Museum of Natural History was the most-visited museum at the Smithsonian with 7.4 million visitors in 2009; attendance at the museum was up 450,000 from 2008. The National Air and Space Museum was the second most-visited Smithsonian museum on the Mall with 7 million visits last year and an additional 1.2 million visitors at its Hazy Center near Dulles airport.

The reopening of the National Museum of American History in late 2008 after an extensive renovation was a big factor in the overall increase in attendance. An estimated 4.4 million visitors came to the museum in 2009, an increase of about 1.4 million visits from 2005, the last full year it was open.

Extended museum hours at the National Museum of American History, the National Air and Space Museum and the National Museum of Natural Historythe three most-visited museums on the National Mallduring summer months also contributed to the surge in attendance.

Attendance figures were also influenced by the release of Night at the Museum 2: Battle of the Smithsonian, which opened in theaters in May. During the summer months, families who had seen the movie asked visitor services staff in the Air and Space Museum where the real things were in the museum.

Attendance figures at the museums are collected by Smithsonian security guards, who use hand clickers to record each person coming in a public entrance. A person who visits several different Smithsonian museums will be counted each time. That is why the Institution uses the term visits, rather than visitors to describe the overall number.

Since the Smithsonians National Zoo is located in a public park and admission is free, annual attendance there is based not on hand tallies but on estimates. This year, it was 2.2 million.